Graphitic Carbon Nitride Nanosheets—Nafion as a Methanol Barrier Hybrid Membrane for Direct Methanol Fuel Cells

Abstract

Sulfonated graphitic carbon nitride (s-GCN) is first realized as an effective bifunctional filler in modifying the Nafion membrane for direct methanol fuel cell (DMFC) application. Carbon nitride with amino (−NH2) and imino (−NH) functional groups was successfully synthesized through one-step calcination of melamine (C3H6N6) and thereafter surface functionalized to incorporate sulfonic acid (−SO3H) groups. The proton transfer in the Nafion–s-GCN hybrid membrane is enhanced by the presence of sulfonic acid groups in the filler and also by acid–base interaction between −NH2 groups present on the GCN with −SO3H groups of hybrid membrane. The Nafion–s-GCN hybrid membrane with an optimized filler content exhibits a proton conductivity of 183 mS cm–1, which is about 36% higher in relation to the pristine Nafion membrane. In addition, porous nature of GCN nanosheets in the hybrid membrane enhances movement of hydronium ions while acting as a barrier for methanol molecule. As a result, the Nafion–s-GCN hybrid membranes displayed much lower methanol crossover current density than that of the pristine Nafion membrane. The DMFC comprising Nafion–s-GCN (0.5 wt %) hybrid membrane delivers a peak power density of 125 mW cm–2 at 70 °C under ambient pressure, while a peak power density of 65 mW cm–2 is realized for pristine Nafion membrane under similar operating conditions.

Graphitic carbon nitride and polymers: a mutual combination for advanced properties

“…130,131 Regarding these challenges, researchers introduced g-C 3 N 4 nanosheets to the polymer matrix. 132 One particular reason to employ a combination with g-C 3 N 4 is its decent thermal stability with chemical bond energy of C-N and CQN of 305 kJ mol À1 and 615 kJ mol À1 , respectively. 133 Another reason is that the amino (-NH 2 ) and imino (-NH) groups of g-C 3 N 4 can interact with acid groups in the polymer matrix, which leads to enhancement of the Grotthuss-mechanism proton transfer.…”

Ameliorated Performance of Sulfonated Poly(Arylene Ether Sulfone) Block Copolymers with Increased Hydrophilic Oligomer Ratio in Proton-Exchange Membrane Fuel Cells Operating at 80% Relative Humidity

“…Because of these benefits, they are competitive with traditional batteries and combustion engines as clean power sources for automobiles and stationary applications [ 6 , 7 ]. Due to their high ion conductivity and extended chemical stability, perfluorosulfonic acid (PFSA) membranes—especially Nafion—are widely utilized as PEMs for PEMFCs [ 8 , 9 , 10 ]. PFSA membranes are by no means perfect, however.…”

Potential carbon nanomaterials as additives for state-of-the-art Nafion electrolyte in proton-exchange membrane fuel cells: a concise review

“…Nevertheless, the incorporation of FCNs has been demonstrated as one of the best strategies to precluding the fuel crossover by generating tortuous paths through the PEM and for improving the proton conductivity by increasing the density of ionic groups in the PEMs. [92][93][94] Hence, FCN llers must be developed and incorporated into the PEM to achieve competent electrolyte materials for fuel cells. From the literature, most researchers have quantied the fuel crossover through the PEM by linear sweep voltammetry (LSV) using the potentiostat/galvanostat, and the detailed protocols to quantify the fuel crossover of PEM can be found in the literature.…”

“…From the literature, most researchers have quantied the fuel crossover through the PEM by linear sweep voltammetry (LSV) using the potentiostat/galvanostat, and the detailed protocols to quantify the fuel crossover of PEM can be found in the literature. [92][93][94] Determining the limiting current density related to the plateau region is considered one way to calculate the fuel crossover of a PEM. The crossover ux of fuel can be evaluated by the following equation.…”

“…11b) of the Naon/CeO 2 -TiC membrane were signicantly improved, owing to the high mechanical stability of TiC and the radicalscavenging activity of CeO 2 . Parthiban et al 92,161,162 integrated different carbon materials, such as nanoporous carbon, sulfonated graphitic carbon nitride, and sulfonated carbon quantum dots, into a Naon membrane and studied the DMFC properties of the prepared hybrid membranes. Remarkably, the prepared hybrid membranes showed a reduction in methanol crossover and increment in proton conductivity with respect to the neat Naon membrane.…”